Connoisseurship in ruby

Ruby is among the rarest of
all the major precious stones, with only a handful of sources producing
facet qualities in any commercial quantity. An approximate ranking
of important ruby origins is given below. This applies only for the
finest untreated qualities from each source and is but a general
approximation. In other words, a top-quality Thai/Cambodian ruby
can be worth far more than a poor Burma stone.

Quality ranking of rubies by country

Burma: While Mogok is the traditional
source of the world's finest rubies, good stones are rare
even from this fabled area. Pigeon's blood was the
term used to describe the finest Mogok stones (see page
331), but has little meaning today, as so few people have seen
this bird's blood. Mogok-type rubies possess not just red
body color, but, by a freak of nature, red fluorescence, too. In
addition, the best stones contain tiny amounts of light-scattering
rutile silk. It is this combination of features which gives these
rubies their incomparable crimson glow. In Mogok rubies, the color
often occurs in rich patches and swirls, and color zoning can be
a problem. Star stones are common. The shape of Mogok ruby rough
generally yields well-proportioned stones.In
1992, the Mong Hsu mine began producing good material,
but most cut stones are under 2 ct. With the exception
of the material from the Thai/Cambodian border, virtually
any of the sources below can produce material of similar
color. The problem is that material clean enough to facet
is rare.

Vietnam: In the late 1980s, this
material literally exploded on the world gem market. Although Vietnam's
ruby originates from two different mines (Luc Yen and Quy Chau),
both sources display similar characteristics. The best Vietnamese
ruby is equal to anything ever produced in Mogok, and if
it had some history behind it, would probably fetch similar prices.

Sri Lanka: The classic case of giving
a dog a bad name. Some of the world's finest rubies have come
from Sri Lanka's gem gravels, but, because of the erroneous 'pink
sapphire' moniker (see page 402),
they have been largely overlooked. Top-grade Sri Lankan reds are
virtually indistinguishable from their Mogok brethren, but many
stones tend towards purple or pink. As with Sri Lanka sapphires,
color accumulates in large stones and so they can be quite magnificent
in sizes of five ct or more. Due to the bipyramidal shape of the
rough, many stones are cut with overly deep pavilions. This material
is strongly fluorescent and stars are common.

Kenya, Tanzania: Stones from these
sources are magnificent when clean, but facet-grade material is
relatively rare. Like Burma, much of this material is strongly
fluorescent.

Afghanistan: Jagdalek has produced
rubies which rank with the best of Mogok, but facetable material
is in short supply. Similar to Vietnamese rubies, many of these
stones contain small areas of blue color. Strongly fluorescent.

Thailand/Cambodia: This material's
main attribute is its high clarity, but the flat crystal shapes
generally yield overly shallow stones. Due to the high iron content,
which quenches fluorescence, most stones tend to have a garnet-red
color. An additional problem is the total lack of light-scattering
silk inclusions (star stones are not found). Although heat treatment
does make improvements, it is not enough. In Thai rubies, only
those facets where light is totally internally reflected will be
a rich red; the others appear blackish, as with red garnets. Thai
stones are actually less purple than most Burmese rubies. However,
Mogok-type rubies appear red all over the stone. Not only is a
rich red seen in the areas where total internal reflection occurs,
but, due to the red fluorescence and light-scattering silk, other
facets are also red. This glowing red color is what makes Mogok-type
rubies so special. With
the decline in Burma production during the 1962–1990
period, the market became conditioned to Thai/Cambodian
rubies, with some people actually tending to prefer them
(In the land of the blind, the one-eyed man is king). Thai/Cambodian
rubies are acceptable only when good material from the
above sources is not available (see box, page
434).

India: The classic Karnataka (Mysore)
Indian locales produce mainly opaque, low-grade star rubies; recently
better material has been reported from Orissa, but as of 1994,
India remains a fringe source.

Connoisseurship in sapphire

Unlike rubies, for which perfection
is unknown, even at the 5-ct level, large fine sapphires of 100 ct
or more do exist. An approximate ranking of blue sapphires in terms
of origin is given below. As with the ruby origin rankings, this
applies only for the finest untreated qualities from each source
and is but a crude measure. In other words, a top-quality Australian
sapphire can easily be worth more than a poor Kashmir stone.

Figure 10.8 21.09
carats of Burmese midnight-blue mystery. This stone, an
example of Mogok's finest product, was offered in
the late 1980s in Bangkok for $10,000/ct. (Photo: Adisorn
Studio, Bangkok)

Kashmir (India): In the world of
blue sapphire, Kashmir is the peak, the quality against which all
others are measured. Kashmir sapphires are noted for their rich
blue hue and distinctive "velvety" luster, caused by
the presence of minute exsolved inclusions. The Kashmir mine, however,
produced in quantity only during the years 1881–1890, and
has produced little since. For this reason, Kashmir sapphires are
generally available only through the estate/auction market. Star
stones have been reported, but are rare. Much Kashmir material
is strongly color zoned and the bipyramidal habit results in overly
deep stones. Thus it can bear a strong resemblance to that from
Sri Lanka. Many old Kashmir stones were cut as sugarloaf cabochons.

Burma: Next to Kashmir, Mogok sapphires
are unsurpassed. Although certain Sri Lankan sapphires may rival
them in beauty, the Burmese stones are of a deeper, richer color,
there being simply more color inside those from Mogok. Moreover,
the Mogok stones do not require heat treatment for their beauty,
but come out of the ground in living color, a blaze of smoldering,
imperial blue. Many fine star sapphires have been found in the
Mogok area, some of large size. Crystal habit in Mogok sapphires
tends to be more tabular than either Sri Lanka or Kashmir. Thus
faceted stones are not so bottom heavy.

Sri Lanka: For those who prefer slightly
lighter, livelier colors, Sri Lanka is the locality of choice.
Blue sapphires from Sri Lanka have a unique beauty all their own,
the best being a sharp, electric blue. Rakwana stones are of particular
note, with their color compared to that found on the tip of a peacock's
feather, or that on a peacock's neck, but fine stones are
found in many places. Until the spread of heat treatments in the
late 1970s, Sri Lankan sapphires commonly reached the richer blues
only in stones of ten carats or more. Today deep blues of all sizes
are common. Sri Lanka is the world's most prolific producer
of giant sapphires (>100 ct). While Mogok stones tend towards
a more intense, royal blue, the Sri Lankan sapphire is typically
a brighter, cornflower blue, due to less color in the stone. Sri
Lanka also produces fine star sapphires, some weighing hundreds
of carats, and is the greatest producer of star corundums of all
colors. As with all Sri Lankan gems, cutting can be a problem.
The typical bipyramidal habit and over-emphasis on weight retention
often result in bottom-heavy stones.

All other sources (alphabetically)
Australia: Australia is one of the biggest producers of faceted sapphire,
but most are dark and inky in color and require heat treatment. The mines
of New South Wales produce the better stones, while the Queensland production
consists mostly of darker blues. Australian sapphires suffer from bad press.
While good quality stones, which can compete with the better Thai and Cambodian
material, are occasionally found, they are inevitably sold as anything but
Australian.Cambodia (Pailin): The Pailin mine in Cambodia has
produced a number of fine stones over the past 100 years,
although today production is limited, due to political
problems. Pailin stones, however, tend to be on the dark
side and faceted stones larger than five carats are rare.
This is in contrast to Kashmir and Mogok, which have produced
a number of sapphire giants. The material is good for cutting
stones below two carats, but even the best Cambodian material
cannot compete with the best from Kashmir, Mogok, or Sri
Lanka. This source has a particular "romance" aspect
to it that is not supported by actual quality.China: Material comes from a variety of different
locales, but all is iron-rich and tends to be overly dark.Nigeria: Nigerian material is also iron-rich and
tends to be overly dark.Thailand: In Thailand, the occasional fine stone
is produced, particularly from the mines of Bo Ploi, in
Kanchanaburi Province. Bo Ploi stones may be of fine color
and sometimes reach sizes of 50 ct or more, but most are
marred by a certain cloudiness. Many Bo Ploi stones are
sold as Sri Lankan, due to their strong color zoning. Sapphires
from Chanthaburi and Phrae tend to be overly dark, although
some are nice.USA (Montana): Yogo Gulch in Montana produces sapphires
of fine color when found in sizes of greater than one carat,
but such stones are extremely rare. The lack of larger
stones (one carat or more) and the flat crystal habit (which
results in low cutting yields), has kept Yogo from being
a source of major importance. Material displays extremely
uniform coloration. Most is cut as round brilliants. Other
Montana localities produce mainly fancy colors, although
heat treatment has changed this somewhat.

Compared
to Kashmir, Burma and Sri Lanka, all other sapphires sources are
of relatively minor importance for high-end stones.

Fancy sapphires

The term fancy sapphire is
used to describe corundums other than red or blue. Sri Lanka is king
of the hill. Within this small island are found sapphires of virtually
every color, including some for which the island is the definitive
source, such as the lovely pink-orange padparadscha. Tanzania's
Umba Valley is also noted for fancy sapphires, as are Montana's
mines (non-Yogo).

Yellow & orange
sapphire

Yellow
sapphires from Sri Lanka are generally of a light to medium
hue, without any brownish overtones. Deeper hues are, like
the Sri Lankan blues, reached only in larger sizes, or via
heat treatment. Heat treatment produces deeper yellows, golds
and oranges that are virtually unknown, or rare in nature.
The very rare pinkish orange padparadscha sapphire
is found mainly in Sri Lanka and at Vietnam's Quy Chau
mines. While similar gems are sometimes found at Tanzania's
Umba mines, most from this locality tend towards the brownish
orange. Padparadschas from Sri Lanka sometimes fetch prices
that rival even ruby.

The
color purple

It
is a common, but erroneous, belief among many traders
and gemologists that Thai/Cambodian rubies are more "purple" than
those from Mogok. Using the proper definition of the
term purple (i.e., a hue or hues lying between red and
violet), we actually find that Mogok rubies are more
purple than those from the Thai/Cambodian border.
Gem dealers know what they are seeing, but do not describe
it in terms consistent with the use of those same words
in other industries. To the color scientist, purple is
merely a hue position. In order to properly describe
the color, saturation and darkness must also be defined.

The
problem with most dealer descriptions of
gem colors is that they try to describe
all colors and color differences in terms
of changes in hue position and darkness.
In fact, when judging the color of gems,
saturation of hue is of paramount importance,
not tiny nuances in hue position. When
a gem dealer says that a Thai/Cambodian
ruby is too purple compared to those from
Mogok, he is confusing the low-saturation
red (grayish red) of the Thai ruby with
the higher saturation (but more purplish)
red of the Mogok ruby.

Figure
10.9 Which
of the above colors is more purple? The
answer is neither. Both colors have identical
hue positions. However there are differences
in darkness and saturation. The color at
left has a darkness of 50% and saturation
of 100%, while the darkness and saturation
values of the color at right are 68% and
63% respectively.

Thailand
and Australia both produce fine yellow sapphires, with the stones
from Chanthaburi in Thailand grading into the highly desirable Mekong
Whisky golden yellow to orange colors. These bring high prices
locally in Thailand and are quite beautiful. Australian yellow sapphires
tend to be overly greenish, although fine golden yellows are found
in the Queensland mines. Sri Lanka, Thailand and Australia are the
only sources which produce deep yellow sapphires in any quantity,
although the Mogok area produces the occasional stone.

Green
sapphire

The
finest green sapphires come from Sri Lanka, but are extremely
rare. These stones tend to be of a lighter and more lively
green than those from Thailand and Australia. The latter two
countries do produce good green sapphires, but most tend towards
an impure blue-green or yellow-green which is not very attractive.
Green sapphires of good color and clarity over 10 ct in size
are relatively scarce, but demand is slow.

Violet
and purple sapphire

Violet
and purple sapphires are found mostly in places which produce
both ruby and blue sapphire. The finest stones come from Mogok,
Sri Lanka and Vietnam. Purple stones bordering on ruby color
are most valuable and may reach prices approaching those of
ruby. Star stones are possible, but relatively rare.

Color-changing
sapphire

Among
the most unusual sapphires are those which display a change
of color. These are judged by the quality of color change,
the best going from the green side of blue in daylight to a
reddish purple in incandescent light. A number of sources produce
such stones, but fine examples are rare. The best are colored
by vanadium (just like the Verneuil synthetic corundums) and
come from Mogok and Umba, Tanzania. These are extremely rare.
More common are Sri Lankan gems which contain a mixture of
chromium (red) and iron-titanium (blue). Such stones appear
bluish violet in daylight and purple under incandescent light.
In the author's opinion, these are marginal as color-change
sapphires. Most tanzanite shows a similar color shift.

Judging stars & cabochons

Fine star rubies come mainly from
Mogok and Sri Lanka. While Mogok has the reputation for producing
the best pieces, the world's finest large example, the Rosser
Reeves Star Ruby, was mined in Sri Lanka. [7]
As for the finest star sapphires, they also come from Mogok and Sri
Lanka, particularly the latter. Deeper colors in Sri Lankan stones
are mainly (but not always) found in the larger sizes, where the
color builds due to the longer light paths.

The
best stones will have just enough silk to create the star effect,
but not so much as to harm the transparency and color (see Figure
10.12). Such stones are extremely rare and valuable. As
for black star sapphires, the most valuable are the golden-star
black stars from Chanthaburi, Thailand.

Important
factors in evaluating star rubies and sapphires include the
following:

Color: This is paramount. One can
have an expensive stone with a poor star, but valuable stars of
poor color do not exist. Top-dollar colored gems have top-dollar
color – it's that simple.

Transparency: If the proper amount
of colorant exists in the stone, only good transparency will bring
it out. The so-called 'glass body' is the ideal. Too
much silk means short light paths, which translates into poor,
grayish color.

Star: The star should be complete
and sharp, with no missing or broken legs, and each ray should
extend to the girdle.

Clarity: Silk should not be concentrated
so thick as to harm transparency. Stones containing too much silk
will have rather poor color, as silk diffuses the light. Longer
needles generally produce a better star than the tiny particles
which are sometimes found, but as with all grading, it's the
end product that counts, not the conditions which produce it. Like
all gems, the ideal is totally fracture-free.

Cut: Only proper cutting releases
a gem's beauty. Cabochons need to be cut with medium to
high domes (overly flat domes allow the star to be seen only
from directly above). The base should be smooth (polished or
unpolished), flat (or gently rounded) and the star should be
properly centered when the gem rests on its base. Domes should
be symmetrical, with no flat spots (which distort the star).
Like middle-aged humans, a common problem is excess weight below
the girdle. Ideally, less than 10% of the gem's depth should
lie below the girdle, but this is rarely found. Due to the bipyramidal
shape of many Sri Lankan crystals, local lapidaries often cut
them with 50%, or even 80%, of the total depth below the girdle.
This is unacceptable, for such stones are extremely difficult
to mount in jewelry, and have the face-up size of pieces of much
smaller weight.

Figure 10.12 Judging
stars: It's all in the color
Low-quality stars contain an over-abundance of silk (left photo).
While this makes for a sharp star, transparency, and thus color,
suffers. Good transparency allows longer light paths, and thus, richer
color (right photo). The result is a far more valuable stone.Left: Stars in the collection of
the Royal Ontario Museum. The stone at
left weighs 174.75 ct, while the 193.39-ct Star
of Lanka is shown at right. (Photo:
Royal Ontario Museum)Right: At 101.01 ct, the Star
of Ceylon is representative of a high-quality
star sapphire. Despite the weak star, this
gem's high transparency and fine color
make it far more valuable than the larger,
sharper stars pictured at left. (Photo:
Richard Allen/Alan Chappron)

Ordinary cabochons are evaluated in an
identical manner to star stones, except they have no star. While
it is a general truth that they are cheaper than faceted goods
(because of their typically poorer clarity), cabochons have a special
beauty all their own. What they lack in scintillation, they make
up in color. In fact, the highest total price ever paid for a single
ruby was $5,860,000 for a 38.12-ct Mogok ruby cabochon (Anonymous,
1994).

Figure 10.13 PDCTP – Pretty
Damned Close To Perfect – is how this star sapphire
would be described. This stone is over 20 ct and hails
from Sri Lanka. (Photo: Rattana Angkuanpanit/World Jewels
Trade Center)

Anatomy of the perfect ruby & sapphire

What makes the perfect ruby or
sapphire? The following is the author's somewhat metaphorical
take on perfection as applied to ruby and sapphire:

Color: Overall, a priority. The best
rubies look like someone painted a swath of fluorescent red across
their face. It is a glowing red, diffused throughout the stone,
and derives from the unique property of fine rubies, a rich red
fluorescence to daylight. For blue sapphire, the color should be
a rich blue, verging on the violet, not too light or dark.

Clarity: Generally
eye clean, but with the following caveat: it should have a velvet-like
softness, as opposed to diamond-like transparency.

Cut: It should show the raw material
off to best advantage, without presenting mounting or durability
problems. Look for simplicity of design and execution. As the one
element of the gem influenced by humans, it should bear the visual
signature of its maker. [8]
Like a Miles Davis horn line, the cut should be an exquisite balance
of economy and intensity.

Overall: The best walk the
walk and talk the talk. They wink at you from across the room,
call your name, beckon you closer. When you see them, you are
driven to possess them and will sell your soul, to Devils or
Lords, to call them your own.

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